Data migration is the process of transferring data between storage types, formats, or computer systems. Data migration is typically required when organizations or individuals change computer systems or upgrade to new systems, or when systems merge, such as when the organizations that use them undergo a merger or takeover.
To achieve an effective data migration procedure, data on the old (i.e., source) system is mapped to the new (i.e., target) system providing a design for data extraction and data loading. The design relates old data formats to the new system's formats and requirements. Programmatic data migration may involve many phases but it minimally includes data extraction where data is read from the old system and data loading where data is written to the new system.
After loading into the new system, results are subjected to data verification to determine whether data was accurately translated, is complete, and supports processes in the new system. During verification, there may be a need for a parallel run of both systems to identify areas of disparity and forestall erroneous data loss.